The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Vehicle article carrier systems are used in a wide variety of applications to support articles of various sizes and shapes above an outer body surface of a motor vehicle. Vehicle article carrier systems can be found in use on a wide variety of different types of motor vehicles such as cars, SUVs, trucks, mini-vans, full size vans, etc. Typically a vehicle article carrier makes use of a pair of support rails that are secured to the outer body surface of the vehicle, and typically a roof of the vehicle. The support rails are typically secured parallel to one another and extend along a major longitudinal length of the vehicle. Typically one or more cross bars are supported at their outer ends by the support rails such that the cross bar(s) extend perpendicularly to the support rails and above the roof surface. Articles are then supported on the cross bars so that they are positioned above the roof of the vehicle.
Traditionally the support rails have been formed from aluminum using a conventional extrusion molding process or sometimes a conventional roll forming process. With both of these processes, the formed support rail will be tubular in construction. However, the cross sectional shape of the support rail must remain constant over the full length of the support rail. That is because there presently is no known way to modify an extrusion molding operation or a roll forming operation such that the cross sectional shape of the support rail can be changed at various points along the length of the support rail. As one can appreciate, this limits the design possibilities for the support rails, both from an aesthetics standpoint as well as a structural standpoint. It would be highly desirable to be able to form the support rails from aluminum or steel, in a cost effective manufacturing operation, where the cross sectional shape and/or area of the support rail is varied over its length. The variation in cross sectional shape or cross sectional area could be selected to provide a unique, aerodynamic appearance and shape, or possibly to provide the support rail with a cross sectional shape at various points along its length which significantly increases it strength and rigidity.
A consideration of motor vehicle manufacturers that is growing in importance is the need to strengthen the roof structure of a motor vehicle, and particularly roof structures of passenger cars and trucks. U.S. governmental crash test requirements are growing in stringency and requiring passenger vehicles to meet increasingly demanding roll over resistance crash tests. During such crash tests a force is applied to the edge of a vehicle roof by a hydraulic ram that applies the force typically at a predetermined angle, often between 20-30 degrees to the plane formed by the outer surface of the vehicle roof. The roof must be able to withstand a predetermined force while suffering only a somewhat modest crushing or “caving in” of the roof structure. Federal guidelines presently exist that define the degree of acceptable “crushing” or “caving in” of the roof structure, and as mentioned above these requirements are slated to be increased in stringency over the next few years. Accordingly, there is an immediate and growing need for motor vehicle manufacturers to strengthen the roof structure of their vehicles using any means that does not significantly complicate the construction process or otherwise add significantly to the cost, weight or complexity of the vehicle.